1. Field of the Invention
The present invention relates to a magnetic switch, and more particularly, to a magnetic switch provided with a permanent magnet disposed at an outside of an upper frame and an externally fitted permanent magnet holder to reduce a number of components and facilitate maintenance.
2. Description of the Related Art
In general, as a type of electrical circuit switching device for transferring mechanical drives and current signals using the principle of an electromagnet, a magnetic switch or direct current relay is installed in various facilities, machines, vehicles and the like.
In particular, in case of a relay for electric vehicles, it may be located at a battery system in an electric vehicle such as a hybrid vehicle, a fuel cell vehicle, a golf cart and an electric forklift to perform the role of switching the conductivity of a main current.
A direct current relay for electric vehicles may include a high voltage portion and a low voltage portion. The high voltage (HV) portion is connected to an electric wire or bus bar to take charge of the conduction and blocking of a main current, and the low voltage (LV) portion operates a drive unit to turn on or off the direct current relay. In general, a direct current relay for electric vehicles is located within a battery system.
FIG. 1 illustrates a lateral longitudinal cross-sectional view of a magnetic switch according to the related art, and FIG. 2 illustrates an internal perspective view of an upper frame assembly in FIG. 1.
The configuration of a direct current relay for electric vehicles may include a lower frame 1, an upper frame 2, a pair of fixed contacts 3 and movable contacts 4 installed within the upper frame 2, and an electric actuator 5 installed within the lower frame 1 to drive the movable contacts 4 to allow the switching control of contacts due to an electrical signal. A permanent magnet 6a, 6b is fixed to a permanent magnet holder 7 and provided within the upper frame 2 to effectively control an arc occurring during the blocking of contacts.
The operation during the blocking will be described with reference to FIG. 3. A pair of fixed contacts 3 (3a, 3b) are configured with two main contact terminals to have a positive (+) and a negative (−) polarity. A permanent magnet 6a, 6B installed within the upper frame 2 forms a magnetic field (B), and fixed to a permanent magnet holder (not shown) to provide the path of a magnetic field. A magnetic field (B) generated from the permanent magnet 6a, 6b interacts with a current (+I, −I) to generate a force (+F, −F) of pushing an arc occurring during the switching to an outside, thereby performing the role of reducing the damage of a contact portion.
However, a magnetic switch according to the related art is assembled in such a manner that two permanent magnet holders 7 are pushed and installed into the upper frame 2 in a symmetric manner, and then permanent magnets 6a, 6b are coupled to both end portions of two permanent magnet holders 7, respectively. The reason of providing two permanent magnet holders 7 is that the operation of pushing and installing into the upper frame 2 is difficult with one integrated form of permanent magnet holder 7. In other words, there is a drawback of increasing the number of components and deteriorating the work process.
Furthermore, two permanent magnet holders 7 are pushed and installed into the upper frame 2, which is a plastic injection molded part, thereby causing a problem of suppressing the intrinsic function of permanent magnets 6a, 6b in case where the permanent magnet holders 7 are released therefrom.
Moreover, it is assembled such a manner that the permanent magnets 6a, 6b are fixed to the permanent magnet holders 7 and the permanent magnet holders 7 are pushed and installed into the upper frame 2, thereby deteriorating the disassembly performance and causing a damage on the surrounding parts during the process of performing dismantling operation when the permanent magnets 6a, 6b are removed for maintenance or the like.